The present invention relates to a lock and more particularly relates to a lock suitable for use in a domestic, office or hotel environment or the like, although embodiments of the invention may comprise locks for car doors, or vehicle ignition locks, or locks for windows, patio doors or the like.
There are many situations where locks are utilised where a large number of people may have access to keys of the lock. For example, in an office environment, various members of the staff who work in the office may be provided with keys. If a member of staff has to be dismissed for any reason, even if the member of staff hands in his or her keys it is always possible that they have had copies of the keys made, and thus if the security of the office is to be guaranteed it is necessary, at the present time, to change the locks in order to ensure that no unauthorised person can obtain access to the office.
In a domestic situation, when a person buys a house from another person, even though it is usually understood that the person selling passes over all available keys to the person buying, there is always a doubt that this has been done, and thus most prudent people again change all the locks.
In a hotel situation, each guest who occupies a room has access to the key of the room and may make an unauthorised copy. This certainly reduces the level of security available to successive guests in the same room, and attempts have been made to overcome this problem by utilising electronic locks where an electronic device is provided associated with each lock adapted to "recognise" a particular key, and in response to such recognition of a key, the lock is electrically opened. The functions of such units are mainly controlled access and in the majority of situations do not offer the standard of security as presented in mechanical systems.
A further disadvantage in the hotel situation is that if a "master" key becomes lost, or an unauthorised copy is made, it may then be necessary to change all the locks within the hotel, which can be very costly.
There is a certain requirement for locks having wards of a particularly distinctive design, so that key blanks receivable within the locks may be restricted. Thus, for example, a particular shop may then be able to sell locks which utilise a particularly distinctive blank, and customers will only be able to have keys cut at that single shop. At the present time this would involve manufacturing totally separately locks for sale by a single shop, which is not commercially viable.
Many locks presently available which have keys of very complex pattern, which are usually cylinder locks having pins movable by the key, are such that the lock can only be actuated from one side. This is clearly disadvantageous.
Locks have to be fitted on doors which are either left-hand hung or right-hand hung. If the lock is provided with a chamfered bolt to provide a slamming action, it is customary for the chamfer to be only on one side of the bolt. The lock, as it is manufactured, has to be assembled with the bolt in position, and whilst the bolt will be correctly orientated for a door hung in one sense, it will not be correctly orientated for a door hung in the other sense. Therefore, on approximately 50% of the occasions on which a door lock is mounted on a door is necessary to at least partly disassemble the door lock in order to reverse the orientation of the bolt.